Study On Modal Identification And Damage Diagnosis Of A Model Arch Bridge

ABSTRACT:With the increasing of the loads and passing speeds of the vehicles, a great number of bridges has suffered all kinds of damage with different extents. The damage detection and condition monitoring of bridges become more and more important. In this paper, the damage identification of a single-span arch bridge is studied and some effective damage detection methods for bridges are obtained.The finite element model for the arch bridge is developed and the damage on the main girder and arch rib is simulated by the decreasing of the elemental stiffness. Many modal parameters, including the modal frequency, the mode shapes, the mode curvatures and the mode curvature differences are used to locate damage. The mode curvature difference is proved to be effective to indicate the location of damage.The dynamic response of the bridge under the moving loads and its second derivative are also tried in the damage diagnosis of the model arch bridge. The numerical results indicate that the second derivative and second derivative difference of the maximum dynamic response curve can not only locate damage, but also show the damage extents qualitatively.The dynamic experiments were conducted on the model arch bridge and the dynamic response data was obtained. The first five order modal parameters are respectively acquired by the stochastic subspace identification (SSI) method and the peak picking (PP) method. The identification modes are compared with the theoretical results to prove the efficacy of the SSI method and the PP method.The theory is integrated with the experiments to study the damage of the model arch bridge, so the results are more accurate than the purely theoretical results. Finally, the limitation of the research in the thesis is concluded and the development direction of damage identification theory in the future is envisioned.